Signaling apparatus for telephone-switchboards.



' N. 759,762. PATBNTED MAY 10, 1904.

E. H. SMYTHE.

SIGNALING APPARATUS FOR TELEPHONE SWI'I'GHBOARDS. APPLIUATION FILED SEPT. 14. 190s.

N0 MODEL.

Ililllllfll No. itat/e2.

UNITED STATES atented May 4I, i904.

PATENT OEEICE.

EDWIN H. SMYTHE, OF FREEPORT, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SIGNALING APPARATUS FOR TELEPHONE-SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent No. 759,762, dated May 10, 1904.

Application filed September 14, 1903. Serial No. 173,087. (No model.)

To all whom, it muy concern:

Beit known that I, EDWIN H'. SMYTHE, a citizen of the United States, residing at Freeport, in the county of Stephenson and State of Illinois, have invented a certain new and useful Improvement in Signaling Apparatus for Telephone-Switchboards, of which the following is a full, clear, concise, and exact description.

My invention relates to a divided multiple switchboard, and has for its object to provide an improved signaling system whereby either of the signals at the different switchboard-divisions may be continuously displayed upon a momentary actuation by the subscriber of a controllingswitch at the substation of a line, the withdrawal of the signal being also under the control of the subscriber.

In another application, Serial No. 140,477, filed January 26, 1903, I have described an organization ci' circuits and apparatus for accomplishing this result, and the present application is to be regarded as a modification of and improvement in some particulars upon the invention of said prior application.

In the preferred embodiment of my present invention two line-relays are connected between the free pole of a grounded central battery and the two limbs, respectively, of the telephone-line, each through a back contact ci' thc other relay. Signals, such as incandescent lamps, are connected to the line conductors, respectively, in parallel branches with said relays. The subscriber is provided with keys by which either limb of the line may be connected to ground through a resistance, preferably the resistance of the telephone apparatus, each key being adapted normally to complete a bridge-circuit through said telephone apparatus between the two limbs or' the line, said bridge being controlled, as usual, by a telephone-switch. When one of the limbs of the line is thus grounded, the relay connected in circuit therewith at the central oiice is therefore excited and attracts its armature, connecting the other limb ol the line to earth and cutting off the other relay. The relay which is actuated thus closes a locking-circuit lli for itself through the line and also provides a local circuit for one of the line-signals. The other line-signal, which is connected to the line in multiple with said relay, is shunted out thereby, the resistance of the line, including the apparatus at the substation, being suiiicient to reduce the di'erence of potential across the lamp so shunted to such an extent that said lamp will not be lighted.

The accompanying drawing is a diagram illustrating two subscribers telephone-lines extending from substations to a central oirice, together with a portion of the central-oilice operators equipment, the system being organized and equipped in accordance with my invention.

The two lines indicated are duplicates, and particular description is required of only one. The operators plug-circuit is oi' a type well known in the art and requires no particular description.

The line extends in two limbs or line conductors 1 2 from the substation A to the multiple spring-jacks s' s2 s at the central-o Hice switchboard. The system illustrated is one in which the switchboard is divided into two divisions, at either ot' which calls may bevanswered. Each line is therefore provided with two answering spring-jacks s' s2, one at each switchboard-division- Two line-signals c c2 are likewise provided in association with the answering-jacks, one at each switchboard-division; and the object, stated generally, or' the present invention is to provide means whereby the subscriber may at will cause the display or withdrawal oil either of these line-signals.

The line conductors l 2 of the line are con-r words, each relay when excited cuts off the other relay and completes a locking-circuit for itself through the line to the return-pole of the battery. The signal-lamps 0/ c2 are connected between the free pole of the battery b and the two line conductors 2 1, respectively, in parallel with the line-relayswthat is to say, the lamp c and the relay u2 are connected in parallel branches from the free pole of the battery to the line conductor 2, the branch through relay u2 being controlled at the back contact of relay u, and similarly relay a and lamp c2 are connected in parallel branches from the free pole of the battery to line conductor 1, the branch through relay a. being controlled at the back contact of relay c2.

At the substation two keys f g are provided, as shown, and the telephone apparatus t is included in a bridge connected between the two sides of the line by way of said keys f g, said bridge containing the telephone apparatus controlled in the usual manner by a gravity telephone-switch. Each key consists of a lever, a normally resting contact, and an alternative contact. The levers of the keys form the terminals of the bridge-circuit containing the telephone apparatus. The normal contacts of said keys form the terminals of the line con,

ductors l f2, and the alternative contacts of both keys are connected to ground. Each key should be constructed so that it will make its alternate contact before breaking its normal contact. It may be mentioned here that of course any return-conductor may be substituted for the ground connection shown, and the specification and claims are to be understood accordingly.

The operation of the system, so far as my invention is concerned, is briefly as follows: The subscriber desiring to signal either of the switchboard-divisions Erst removes his telephone from its hook and then actuates one or the other of the keys f g, according to the division to be signaled. In either case one or the other of the line conductors, according to the key which is actuated, is grounded through the resistance of the telephone apparatus. rlhe line-relay at the central oflice in the limb thus grounded is thereupon excited and draws up its armature, cutting off the other relay and connectingthe other limb of the line to the return-pole of the battery. A locking-circuit through the line is thus provided for the relay after the key resumes its normal position, and a local circuit is also provided at the central oflice for the corresponding signal lamp, whereby said lamp is allowed to display its signal. The other lamp is in shunt with the actuated relay, the resistance of the line and the telephone apparatus being in the undivided portion of the circuit, whereby said other lamp is shunted out and does not display its signal. Either signal after being thus displayed can be Withdrawn at will by the subscriber by simply replacing his telephone on its hook, whereby the line-locking circuit of the relay is broken. The telephone-switch cooperates with either key in the transmission of a signal, this being a desirable feature in practice.

It is evident that my invention is not limited to the arrangement whereby the resistance of the telephone apparatus is utilized as the resistance to cut down the electromotive force by which the shunting of one of the lamps by one of the relays is made possible, and, in fact, my invention is capable of various modiications which will readily suggest themselves to those skilled in the art, and it is not to be considered as limited in its application to the particular system shown.

I claim# l. The combination with a telephone-line extending in two limbs from a substation to a divided multiple switchboard, of a central battery having' one pole connected to a returnconductor, two line-signal devices, the two limbs of the line being each connected with the free pole of the battery through a corresponding signal device and a back-contact portion of the vother signal device, and arranged to be connected alternatively through a front-contact portion of such other signal device to the other pole of the battery, and switching means at each substation for opening the circuit of the line and connecting either limb as desired to said return-conductor.

2. The combination with a telephone-line extending in two limbs from a substation to a divided multiple switchboard, of a central battery having one pole grounded, two line-relays normally connected between the free pole of the battery and the two limbs of the line, respectively, each through a back contact of the other relay, front contacts of said relays adapted alternatively to ground the respective limbs of the line, two signals, one at each switchboard-division, connected between the free pole of the battery and the respective limbs of the line, telephone apparatus at the substation, and two calling-keys at the substation adapted to ground either limb of the line through the telephone apparatus and simultaneously to open the other limb.

3. The combination with a metallic-circuit telephone-line extending from a substation to a central oiiice, of a central battery having one pole connected to a return-conductor, two linesignal devices normally connected between the free pole of said battery and the two limbs of the line, respectively, telephone apparatus'in a bridge at the substation, a telephone-switch controlling said bridge, and two keys at the substation, each key having a switchflever, a normal contact and an alternate contact, the said switch-levers being connected to form the terminals respectively of the telephone-bridge, the normal contacts of said switch-levers being connected to form the respective terminals of the two limbs of the line, and the alternate contacts being connected to the aforesaid re- .TOO

IIO

turn-conductor, substantially as and for the purposes set forth.

4. The combination with a telephone-line extending in two limbs from a substation to a central oiiice, of a central battery having one pole grounded, a signal and relay connected in branches from the free pole of said battery to one limb ot' the telephone-line, said relay when excited being adapted to ground the other limb of the telephone-line, a key at the station normally closing the metallic circuit and adapted alternatively to open said circuit and ground the line to which said relay is connected, a resistance in the circuit controlled by said key, whereby upon the actuation of said key the said relay is operated but the signal is shunted thereby, and a second signal displayed by said relay when excited.

5. The combination with a metalliccircuit subscribcrs telephone-line, of a grounded central battery, a line-relay and a signal in parallel branches from the free pole of said battery to one limb of the line, another line relay and signal in parallel branches from said battery-pole to the other limb of the line, each relay having' a normal contact controlling the connection of the other relay to the line, and having' an alternate contact adapted to break said connection and to connect said limb to ground, and switching apparatus at the substation adapted alternatively to complete a bridge-circuit or' the line or to open either limb and ground the other.

6. The combination with a metallic-circuit subscribers telephone-line, of a grounded central battery, a line-relay and a signal in parallel branches from the iree pole of said batmme@ tery to one limb of the line, another line relay and signal in parallel branches from said battery-pole to the other limb of the line, each relay having a normal contact controlling the connection of the other relay to the line, and having an alternate contact adapted to break said connection and to connect said limb to ground, switching apparatus at the substation adapted alternatively to complete a bridge-circuit of the line or to open either limb and groiind the other. and a resistance at the substation included in the circuit of either limb whether completed directly through said switch or through the other limb of the line, whereby each signal is shunted by the relay-magnetin parallel therewith while said relay acts to display the other signal.

7. The combination with a metallic-circuit telephone-line, of a grounded central battery, a relay connected between the free pole of said battery and one limb of the line, a key at the substation adapted to ground said limb and alternatively to complete circuit to the other limb, substation telephone apparatus included in a circuit closed by said keyin either of its alternative positions, asignal in shunt ot' said relay, a front contact oit said relay connected to complete a locking-circuit of said relay through the line, and a second signal arranged to be displayed by said relay when excited.

In witness whereof I hereunto subscribe my name this 21st day of August, A. D. 1903.

EDWIN H. SMYTHE.

Witnesses:

WM. E. Hummm), JonN Gr. Ronnnrrs. 

